Many applications of neurosonography could be extended or improved by the development of a standardized microbubble contrast agent capable of increasing the echo signal from a deep brain target. This research goal was accomplished in vitro during Phase I, and now the Phase II program will, as its first objective, address ultrasonic imaging in vivo through a series of detailed animal validation experiments (or rats) with a high- purity version of the standardized microbubble contrast agent. The second objective of Phase II will be to carry out in vitro modification of the surfactant-stabilized microbubbles to include a "paramagnetic agent" and selected "tumor-targeting" molecules within the surfactant monolayer surrounding the microbubble. As microbubble modifications are accomplished, the third objective is to address NMR imaging of brain tumors and other lesions (through intact skull) by conducting animal validation studies (on rats) with the modified microbubble contrast agents. The last objective of Phase II will be to define generally, via the above animal validation studies, the image processing techniques necessary to correlate pre-operative magnetic resonance images with intra- and post-operative ultrasonic images, in preparation for clinical validation studies and eventual commercialization of the microbubble contrast agents.